: The proposed study aims to develop a new, reliable and more user-acceptable method for treating male impotence by administering prostaglandin E1 through the surface of the penis. Until recently, the most reliable methods involved self-injection, which may evoke needle phobia and involve risk of tissue damage. The recent approvals of a medicated intraurethral prostaglandin suppository and an oral form of sildefanil both offer significant benefits, but the suppository involves the use of an invasive urethral applicator while oral sildefanil is expensive and administered systemically. The applicant, Dr. Nichols, at BIOTEK has provided preliminary data to demonstrate that erectogenic prostaglandin E1 can be delivered transdermally through the external surface of the glans or penis. He has requested support for a Phase I study. Five specific aims have been proposed to 1) prepare and test formulations in vitro using human skin in transdermal permeation tests, 2) conduct studies of penile and vaginal irritation in rabbits, and 3) conduct erectile studies on dogs using the most promising formulation. Phase II will then proceed to develop a convenient method of application, prepare and submit and IND, and conduct a FDA-approved human clinical study of safety and bio-availability. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE